e same feature, _not_ subjected to this
influence, and we have deepened the _effect_ of shade.

Now, the principles by which we are to be guided in the selection of one
or other of these means are of great importance, and must be developed
before we can conclude the investigation of villa architecture.

231. The impression produced by a given effect or influence depends upon
its degree and its duration. Degree always means the proportionate
energy exerted. Duration is either into time, or into space, or into
both. The duration of color is in space alone, forming what is commonly
called extent. The duration of sound is in space and time; the space
being in the size of the waves of air, which give depth to the tone. The
duration of mental emotion is in time alone. Now in all influences, as
is the degree, so is the impression; as is the duration, so is the
effect of the impression; that is, its permanent operation upon the
feelings, or the violence with which it takes possession of our own
faculties and senses, as opposed to the abstract impression of its
existence, without such operation on our own essence.

For example, the natural tendency of darkness or shade is to induce fear
or melancholy. Now, as the degree of the shade, so is the abstract
impression of the existence of shade; but as the duration of shade, so
is the fear or melancholy excited by it.

Consequently, when we wish to increase the abstract impression of the
power of any influence over objects with which we have no connection, we
must increase degree; but, when we wish the impression to produce a
permanent effect upon ourselves, we must increase duration.

Now, degree is always increased by contrast, and duration by
assimilation. A few instances of this will be sufficient.

232. Blue is called a cold color, because it induces a feeling of
coolness to the eye, and is much used by nature in her cold effects.

Supposing that we have painted a storm scene, in desolate country, with
a single miserable cottage somewhere in front; that we have made the
atmosphere and the distance cold and blue, and wish to heighten the
comfortless impression.

There is an old rag hanging out of the window: shall it be red or blue?
If it be red, the piece of warm color will contrast strongly with the
atmosphere; will render its blueness and chilliness immensely more
apparent; will increase the _degree_ of both, and, therefore, the
abstract impression of the existence of c